Poly(arylene sulfide ketone) (henceforth PASK) resins and poly(arylene sulfide diketone) (henceforth PASDK) resins are engineering thermoplastics of potential commercial interest for film, fiber, molding, and/or composite applications because of their outstanding thermal and mechanical properties. General processes for the production of poly(arylene sulfide ketone)s and poly(arylene sulfide diketone)s are known in the art. For example, poly(arylene sulfide ketone)s or poly(arylene sulfide diketone)s can be prepared by the reaction of an alkali metal sulfide in a polar organic compound with a polyhaloaromatic ketone or a polyhaloaromatic diketone, respectively.
A major disadvantage often associated with the production of poly(arylene sulfide ketone)s and poly (arylene sulfide diketone)s pertains to the particle size of the polymeric particles produced. Generally, at the completion of the polymerization reaction, the reaction mixture is a slurry comprising a liquid phase (predominantly a polar organic compound and water) with a solid phase dispersed therein (predominantly polymeric resin). This slurry filters very slowly and, thus, hampers the polymer's washing, recovery, and handling processes. When the polymer is recovered by usual methods, it is ordinarily in the form of powder-like particles having very low bulk densities (e.g. generally less than 10 lbs/ft.sup.3). Recovery, processing and handling of PASK and PASDK resins which have low bulk densities and are in a powder-like form are extremely difficult.
Extreme difficulty in feeding an extruder with this low bulk density powder-like resin has also been experienced. Efforts to force feed an extruder with an auger-fed hopper does not overcome these difficulties, nor does compacting the powder, such as in a heated 2-roll mill. Furthermore, the fine particle size introduces a non-systematic error in the determination of the melt flow of the polymeric resins. Variations in the time required to load the barrel of the melt flow apparatus with low bulk density powder produces an uncertainty in the test results since PASK and PASDK require high temperatures for melt viscosity determinations; and those high temperatures may compromise melt stability of the polymers under the measurement conditions.
Other problems which are inherent with low bulk density resins pertain to commercial plant operations, such as production and storage capacities and/or environmental concerns. Specifically, since production and storage vessels in a commercial plant have a constant volume associated therewith, as the bulk density of a polymeric resin decreases, so does the production and storage capacity of the commercial plant. Therefore, if the bulk density of a polymeric resin can be increased, the production and storage capacities of the commercial plant would also increase.
As for environmental concerns, a low bulk density resin which is in a form of a powder would have a greater tendency of being dispersed through the air of the working environment during downstream processing and handling procedures than would a similar polymeric resin having a higher bulk density. Therefore, providing a polymeric resin having an increased bulk density would improve the environmental conditions which are associated with the handling and processing of such a resin.
Treating powder-like PASK and PASDK resins in a manner which produces granular resin particles having bulk densities greater than their untreated counterparts would greatly improve the recovery and processability of these resins. Therefore, one object of this invention is to provide a method for treating PASK and PASDK resins in a manner which produces granular particles having bulk densities greater than their untreated counterparts, wherein the handling, filterability and processability of the respective polymeric resins are improved.
The internal pressures in polymerization process vessels during typical polymerization reactions are generally high (e.g., above about 100 psig). Safety risks and economic concerns are often associated with excessively high polymerization reactor pressures. For instance as the internal pressure of a polymerization process vessel increases, the risk of potential safety hazards increases, as does the cost of designing and/or fabricating this process vessel.
When designing, purchasing and/or fabricating polymerization process vessels, one does so with the understanding that the polymerization process for which it will be employed will generate pressures falling within a specific range. Therefore, although a process to provide higher bulk density PASK or PASDK resins which have associated therewith improved processability is desirable, the desirability of such a process may decrease if it results in generating pressures within a polymerization process vessel which were in excess of the vessel's operable range.
It is yet a further object of this invention to provide more granular, higher bulk density particulate PASK or PASDK resins having associated therewith improved processability without generating pressures significantly greater than those generated during polymerization reactions of PASK or PASDK resins.
Other aspects, concepts, and objects of this invention will become apparent from the following detailed description and the appended claims.